Lava vapor-tube.



J. L. R. HAYDEN.

LAVA VAPOR TUBE.

APPLICATION FILED AUG. 9, 1907.

Wit/76556 8M im/L/ 7' To all whom it may concern:

STATES PATENT oFFIoE.

JOSEPH L. It. HAYDEN, OF SOHENECTAIDY, NEW YORK, ASSIGNOB TO GENERAL ELECTRIC COMPANY, A. CORPORATION OF NEW YORK.

. LAVA VAPOR-TUBE.-

Specification of Letters Patent.

Patented Dec- 17, 1912.

Be it known that I, JosEPn LE Roy HAYDEN, a citizen ofthe United States, re-

siding at Schenectady, county of Schenectady, State of New York, have invented certain new and useful Improvements in Lava Vapor-Tubes, of which the following 15 a specification.

Vapor electric devices, such as mercury lamps and rectifiers, ordinarily comprlse an evacuated envelop of glass in which the elec-- trodes of the device are mounted. When the quantity of current is considerable, the envelop is commonly provided with an enlarge ment to operate as a condensing chamber for condensing vapors given oil by the cathode during normal operation. The con densing action produced within the tube is due to radiation of heat by the condensing chamber, and therefore if the currentis heavy, the condensing chamber must be large. Artificial cooling, such as water circulation cannot ordinarily be used, as the glasswill not stand the temperature differences and variations. Very large condensing chambers of glass are subject to breakage from other causes, such as impact of mercury on the glass during transportation, oreven from the pressure of the atmosphere.

According to my invention, the tube of the vapor device is built of material which will permit artificial cooling, which will not crack from violent changes in temperature, and which is otherwise suited for use as the envelop of a vapor device. I find that lava or burned steatite (magnesium silicate) can be made into envelops having the qualities above mentioned. This material is inexpensive, can be readily machined, and furthermore, does not conduct electricity and does not amalgamate or otherwise combine with mercury or mercury vapor. In the last mentioned respects, it difiers radically from iron, which, when used as the entire envelop of a mercury vapor device, contaminates the mercury and makes it scummy.

Lava rectifiers maybe made in two distinct ways, either by cutting the tube or its parts from solid stone, or by pressing or molding the tube from powdered steatite mixed with abinder, such as clay or a high hydrate of magnesium silicate. The former is in my opinion the better process, though when the rectifier is of large size it can advantageously be made of several pieces put together. Rectifiers cut from the solid stone are much heavier and denser than those molded from the owdered material. The molding process a ove described forms no part of my invention.

Steatite or raw lava, can be drilled and machined with ease, and then, b baking at a high temperature, can be ma e hard and soli Tubes or" envelops for vapor devices may be of a great variety of shapes, but one form of tube embodying my invention is shown in thelaccompanying drawing in which Figure 1 is a sectional elevation and Fig. 2 a detail.

The apparatus illustrated consists of a tubular vessel 1 cut from a solid block of steatite and provided at the bottom with a contracted portion serving as a receptacle for the mercury cathode 2 of the rectifier. On either side the cathode 2' is placed a tubular well closed at the bottom in a manner hereinafter described and serving as a receptacle for the mercury of auxiliary anodes '3 and 4. The top of-the tubular envelop 1 is closed by means. of a screw threaded lava plate 5 having a depending chamber 6 projecting downward a substantial distance within the envelop 1 and serving to 85' convert the s ace within the envelop into an annular c annel communicating along its lower edge with the space immediately adjacent the cathode 2. Within the annular channel formed between the chamber 6 and 90 envelop 1 are mounted the main anodes 7 and 8 of the vapor device. These anodesmay be of graphite or other suitable material having a fluted surface and ma be carried on leading-in conductors 9 0 iron or other suitable material.

The several openings into the vapor device are closed with metal caps 10, each of which consists of thin sheet metal, such as iron, and fits tightly over the end of a tubular projection of the lava. v To insure a vacuum tight joint between the-metal caps and its lava tube, I first proceed by coating the tube with v blue glaze of a typecommonly used for enameling iron, and then heat the entire device in a blast furnace to cause the glaze to soak in between the iron and lava. To facilitate this action of the glaze, the. iron cap 1 may be slightly flared at its edges. Whenthe joint cools, the glaze solidifies and 110 the iron cap shrinks tightly on the gives a vacuum tight joint. I find that this joint remains tight even when fs'ixbjected to sembled, and then screw the parts together,

while maintaining the enamel in a heated and fluid condition. The enamel then herdens in the threads and gives a tight joint.

A V shaped groove above'the threads may be filled with enamel or with mercury. In case the rectifier is to 'be'taken a art, the joint can be heated beyond the melting point of the enamel and then unscrewed. I 2 As an alternative method of connecting the end closure 5 with the tubular member 1 of the envelop, I may weld the parts directly together by using an oxygen flame or an arc blast. The surface of the lava melts and flows andso welds over the joint.

I find that lava tubes, even when made from first class steatite and baked at the highest temperatures, are somewhat porous and are liable to slow leaks through the walls themselves- I therefore consider advisable the glazin of the entire rectifier tube. One way'lo doing this consistsin melting the surface of the lava by. means of an oxygen flame, oran arc blast, until the surface is uniformly melted over the entire tube. As a preliminary step to this process, I shrink the lava by baking for a considerable time at a temperature as near the melting point as is safe. The glaze or melted lava, above described, is intimately joined with the material of the tube, and so has no tendency to crack or flake.

As an alternative method of preventing slow leaks through the envelop, I may coat it with blue enamel ofthe well known com-- position. I find this flows nicely over the lava surface and gives it a vacuum tight glaze; It is even possible to glaze the surace in much the same way that porcelain is glazed, by putting on a coat, such as steatite with a small percentage of potassium silicate, or the feldspar usedin'porcelain glazing, and then melting-and baking, with porcelain. In applying enamel or other coating toga lava rectifier I may first put the whole rectifier together then put on the melted. enamel, and final y connect the de-' vice to the vacuum pump and so suck the enamel in whereverv pores orjoints may exist. I

As a convenient means for connecting the vapor'gdevice with a racmuunrmp ...u i,1 U

joint between a small iron from one of the iron gaps at the anode end of the device. During exhaustion, the rectifier should be heated to a very high temperature so that' all gases may be driven out of the walls of the envelop. A very considerable quantity ofgas comes off at first, but by continuing the pumping, the lava is almost completely freed from gas.

Prior to sealing off from the pum the temeratureof the rectifier is lowere mercury islet in and the mercury are started. After the arc has been in o eration for a time, the tube is disconnected rom the pump by sealing off the iron connecting tube 12 by the use of an oxygen flame.

[The downwardly projecting chamber 6 u may be utilized asa receptacle for a cooling fluid 1 3 and will serve to keep down the temperature of the rectifier even when it is operated on very high currents. I find that the lava tubes will not break, even though subjected to very rapid and very great temperature changes. The, rectifier tube may even attain a red-heatand then he suddenly cooled in water without danger, of cracking.

One marked advantage of artificialxcooling, such as, water circulation, is. that the rectifier may be small in volume and still carry a very heavy current. In this respct the lava rectifier is quite different from the ordinary self cooled rectifier with a glass envelop.

Fig 2 illustrates a modified form of anode over the end of a downwardly projecting lava tube 15 and connected with the circuits of the system by means of a body of mercury 16 carried within the lava tube. This body of mercury also serves to insure a vacum'n' tight joint between the lava tube and the iron cap I4.

What I'claim as new and desire to secure by Letters Patent of the UnitedStates, is,-

1. An envelop for vapor electric devices consisting essentially of glazed lava.

2. An envelop for vapor electric devices consisting essentially of. self lazed lava.

3. An envelop for vapor e ectric devices, consisting of a plurality of glazed lava parts joined together, and a seal for said joints consisting of vitrified lava. 'In witness whereof, I have hereunto set my hand this 8th day of August,'1 907.

JOSEPH L. R. HAYDEN.

Wit'nesses:

BENJAMIN B. HULL,

.I'I N 

